starlette/docs/applications.md

Starlette includes an application class Starlette that nicely ties together all of its other functionality.

from contextlib import asynccontextmanager

from starlette.applications import Starlette
from starlette.responses import PlainTextResponse
from starlette.routing import Route, Mount, WebSocketRoute
from starlette.staticfiles import StaticFiles


def homepage(request):
    return PlainTextResponse('Hello, world!')

def user_me(request):
    username = "John Doe"
    return PlainTextResponse('Hello, %s!' % username)

def user(request):
    username = request.path_params['username']
    return PlainTextResponse('Hello, %s!' % username)

async def websocket_endpoint(websocket):
    await websocket.accept()
    await websocket.send_text('Hello, websocket!')
    await websocket.close()

@asynccontextmanager
async def lifespan(app):
    print('Startup')
    yield
    print('Shutdown')


routes = [
    Route('/', homepage),
    Route('/user/me', user_me),
    Route('/user/{username}', user),
    WebSocketRoute('/ws', websocket_endpoint),
    Mount('/static', StaticFiles(directory="static")),
]

app = Starlette(debug=True, routes=routes, lifespan=lifespan)

??? abstract "API Reference" ::: starlette.applications.Starlette options: parameter_headings: false show_root_heading: true heading_level: 3 filters: - "init"

Storing state on the app instance

You can store arbitrary extra state on the application instance, using the generic app.state attribute.

For example:

app.state.ADMIN_EMAIL = 'admin@example.org'

Accessing the app instance

Where a request is available (i.e. endpoints and middleware), the app is available on request.app.